Fumigation with fluorocyclobutenes



2,779,680 FIMGATION WITH FLUOROCYCLOBUTENES Mark A. Wolf, Midland, Mich., assignor to The Dow Chemical Company, Midland, Micl1., a corporation of Delaware No Drawing. Application June 30,1953, Serial No. 365,240

Claims. (Cl. 99-153) The present invention relates to fumigation and is particularly concerned with an improved method and composition for the fumigation of grain and its milled products for the control of infesting insects, bacteria, fungi and nematodes.

The application of fumigant materials offers an excel lent method for the control of insects, bacteria and fungi in grain and its milled products. However, the utilization ofsuch a method has been severely restricted by the inability of many fumigant materials to penetrate in lethal concentrations to any substantial depth in grain and flour. The use of others of the known fumigant materials has been most generally hampered by the disagreeable odor and flavor characteristics which they impart to matter fumigated. Thus, the hazard of off-flavor and ill-smelling grain and flour has curtailed wide-spread employment of many such materials. These shortcomings of known treatment methods have created special difiiculties in the fumigation of grain and its milled products.

It is an object of the present invention to provide a new and improved method of fumigation for the control of nematodes, bacteria, fungi and insects. It is a further object to provide an improved method and composition for the fumigation of grain and its milled products. Another object is the provision of a method and composition which will accomplish superior penetration of grain and its milled products. An additional object is the provision of a method which does not impart an oif-taste or oflensive odor to fumigated materials or adversely affect the germination of grain. Other objects will become apparent from the following specification and claims.

According to the present invention it has been discovered that matter infected or infested with bacteria, fungi, nematodes and insects advantageously may be fumigated and the organisms killed by treatment with hexafluorocyclobutene, 1-chloro-2,3,3,4,4-pentafluorocyclobutene or 1,2-dichloro-3,3,4,4-tetrafluorocyclobutene. More particularly, it has been discovered that grain and its milled products and other food stuffs may be fumigated with or exposed to the vapors of these fluorine compounds to control bacteria, fungi and insects without imparting undesirable taste or odor characteristics to the fumigated products. Such fumigation operations are carried out in an enclosed space or otherwise to insure a suflicient period of contact of the furnigant with the infesting organisms. The cyclobutene compounds are non-flammable, gaseous or liquid materials at ordinary temperatures, which are somewhat soluble in many organic solvents but have a very low solubility in water. They are adapted to be easily and conveniently employed for the fumigation of grain and its milled products.

The compounds have very desirable penetrating prop-- erties which enable their vapors to diffuse through and permeate in parasiticidal concentrations the interstices of grain and its milled products to an extreme depth and within a relatively short period of time.

nited States Patent 0 The exposure of bacteria, fungi, nematodes or insects to at least a minimum effective dosage of the fluorine compounds is essential for the practice of the present invention. In general, this dosage is employed in an enclosed space and amounts to a lethal or parasiticidal concentration. When fumigating grain and its milled products, good results are obtained when the, fluorine compounds are employed in an amount corresponding to at least 0.2 pound per thousand cubic feet of space Within which the product is enclosed. Alternatively, the fumigation of soil or other growth media may entail the injection of the fluorine compounds or solutions thereof under the surface of the soil followed by rolling or wetting the surface of the treated soil to provide a seal.

In carrying out the present invention, the matter to be fumigated may be exposed to the vapors of the fluorine compounds in any convenient manner. When fumigating grain, the grain is placed in an enclosure together with the required amount of fluorine compound. When the employed fluorine compound is a liquid, it may be poured upon the surface of the grain and/or introduced at various levels therein. If the fluorine compound is a gas at ordinary temperatures, it may be introduced generally into the enclosure or at various levels within the grain. In the fumigation of flour and milled grain products, the latter are generally bagged and thereafter placed in an enclosure together with the required amount of fumigant material in vapor or vaporizable form. 'In such operations, the liquid fluorine compound is generally placed in shallow pans or sprayed upon the walls or other surfaces within the enclosure. The compound readily volatilizes from the surfaces upon which it is distributed to provide the required minimum concentration of 0.2 pound per thousand cubic feet of space. The exposure of the infested material and undesired organisms may be carried out in some other gas than air, e. g. nitrogen or carbon dioxide.

In an alternative method, the fluorine compounds are dissolved or otherwise incorporated in an inert volatile organic solvent such as acetone or volatile liquid haloaliphatic compound or volatile petroleum distillate and the resulting mixtures employed in the manner as previously described. The preferred organic solvent carriers are those of such volatility that they evaporate from the matter treated and leave little permanent residue therein. The exact concentration of the fluorine compounds to be employed in these solvent fumigant compositions is not critical. The required dosage of the fluorine compounds generally may be supplied with compositions containing from 1 to 90 percent by weight of toxicant.

A preferred embodiment of the invention consists of a petroleum distillate solution of the fluorine compounds. The petroleum distillatesto be employed in such embodiment are carefully cut portions boiling almost entirely under 400 F. at atmospheric pressure and having a flash point above about F. These fumigant compositions are of particular value for the fumigation of soil and are characterized by having excellent penetrating properties.

In another preferred embodiment, the fluorine compounds are incorporated in lowboiling volatile organic solvents, which-change to gases when released from a confined space,' to prepare self-propellant fumigant compositions. Such compositions may be prepared by mix ing a liquefied gas such as carbon dioxide, dichlorodifluoromethane, methyl chloride, etc. with the fluorine compound in a sealed container or cylinder. These selfpropellant compositions are of particular value and convenience for the fumigation of food stuflfs normally pack aged in cellulosic or plastic Wrappers.

Other materials which maybe combined with the fluorine compounds, either as volatile solvents or as supplementary toxicants or both, include carbon tetrachloride, ethylene bromide, ethylene chloride, hydrogen cyanide, trichlorobromomethane, carbon bisulfide, acrylonitrile, tetrachloroethylene, trichloromethylene, chloropicrin methylbromide, beta,beta'-dichloro-ethyl ether and propylene chloride. These compositions are of outstanding value for the fumigation of infested material where superior penetrating properties are desired. Alternatively, such compositions may be dissolved or otherwise incorporated in an inert organic solvent and the latter composition employed in the present method as previously described. i e 7 According to the present invention, grain and its milled products are generally exposed to the vapors for a period of at ieast two hours or longer, the exact period of time being dependent upon the nature and size of the treating chamber and the ease with which the vapors may penetrate the product to be fumigated, e. g;, Whether grain 0.1

flour is concerned. In small enclosures, exposures from a few minutes to a few hours may be suflicient to accomplish penetration and the killing of the organism. In large enclosures and with large quantities of grain and its milled, products, periods up to 72 hours or longer may be desirable.

The following examples illustrate the invention but are not to be construed as limiting:

Example 1 1,2-dichloro-3,3,4,4-tetrafluorocyclobutene (boiling at 67.1 C. at 760 millimeters pressure) and hexafluorocyclobutene (boiling at l.l C. at 760 millimeters pressure) were separately employed for the fumigation of an enclosure, the interior walls and surfaces of which were infested with adult confused flour beetles (Tribolium con- Example 2 In an exactly similar operation, these cyclobutenes compounds were separately employed for the control of black carpet beetle pupae (Atmgenits piceus). .As a .result of such operations, 10.0 percent kills-of beetles were obtained with a concentration of-"0.5 pound .of the 1,2- dichloro-.3,3,4,4-tetrafluorocyclobutene and the hexafluorocyclobutene per 1000 cubic feet. I

Example 3 V l-chloro-2,3,3,4,4-pentafluorocyelgbutene isintroduced into an airtight bin of oats inan amount sufficientto provide a concentration of 1.5 pounds of the vapor of the .fiuorine compound per 1000 cubic feet. The oats are stored in the bin to a depth of about 6 feet. Prior to the introduction of the fluorine compound, the cats are infested at different levels with adult confused flour beetles and black carpet beetle pupae. After'three days exposurev at :an average temperature of about 75 R, a complete kill of the infesting insects is observed at all levels in the oats. Two weeks after the fumigation, no evidence of off-taste or offensive odor, attributable to the action of the fluorine compound, is found in the fumigated oats.

' Example 4 p Hexafluorocyclobutene and 1,2-dichloro-3,3,4,4-cyclobutene were separately employed for the furnigation'of corn. In such operations, the corn was placed in a fumigant chamber together with a measuredamount of a cyclobutene compound andthecorn then-mixed for a period Tare/9,680 V 7 of time to accomplish distribution through the corn of the vapors of the compound. Following the agitation period granary weevils (Sitophilus granarius) were introduced into the grain and the exposure to the vapors thereafter continued for a period of 16 hours. The concentrations at which the compounds were employed together with the controls obtained are set forth in the following table;

One week after the fumigation, no evidence of off-taste or offensive odor, attributable to the action of the fluorine compounds, is found in the furnigate'd corn.

' Example 5 The cyclobutene compounds were also separately employed for the fumigation of wheat 1 In Such p tions, the flour was placed in a fumigant chamber and a cyclobutene compound introduced into the chamber in an amount sufficient to provide a concentration of 0.5 pound per 1000 cubic feet. Prior to the introduction of the toxicant, the flour was infested with adult confused flour beetles at a depth of about 9 inches within the finely milled product. In each determination the flour was exposed to the vapors of the employed compound for about 16 hours. As a result of the determinations, hexafluorocyclobutene and 1,2 dichloro 3,3,4,4 tetrafluorocyclobutene were found to give a 1.00 percent kill of the infesting organisms at a depth of 9 inches within the flour. Sensory examination and inspection of the flour, one week following the exposure, showed no evidence of off-taste or offensive odor attributable to the action of the cyclobutene compounds.

Example 6 A furnigant composition, having a flash point greater than F., is prepared by mixing together 20 percent by volume of 1,2-dichloro-3,3,4,4-tetrafluorocyclobutene and 30 percent of a petroleum fraction commonly known as Stoddards solvent. The latter solvent has a boiling range of from 325 to 400 F. and a flash point of about 116 F. This composition is emplollfitl for the treatment of a seed bed containing a sandy loam soil which is in.- festcd with root knot nematodes. in the treating opera-- tiona, the distribution is accomplished by infecting the fumigant mixture into the soil in ro'wsz8 inches apart, the injections being made at 4 inch intewals and at a depth of about 6 inches below the soil surface. The amount 7 fumigant material employed is sufiicient' ,to supply 15.0 pounds of toxicant per acre. Following the distribution of the fumigant, the soil surface-is sealed with'ahoiut one acre inch of water. a

One month later, the seed bed is planted with tomato seeds. Four weeks after planting, the tomato seedlings are lifted from the soil, their roots washed, and the latter examined for gall formation attributable to nematode attack. As a result of these operations, there i-isfound a commercial control of nematodes.

Example had adversely affected germination. The determinations showed that the fumigation operations had not adversely affected the germination of the corn.

Example 8 with a valve dispersing a measured portion of the fumigant mixture through a needle orifice into each packaged food container. The furnigant composition is employed in an amount sutlicient to provide in each package a concentration of the fluorine compound equivalent to 0.3 pound per 1000 cubic feet. Following the introduction of the fumigant, the discharge needle is withdrawn from the package and the perforation sealed. The fumigated raisins and unfumigated but similarly packaged raisins are then stored at an average temperature of about 70 F. After two months of storage, various of the fumigated and unfumigated packages are selected at random and examined for the development of mold and mildew on the packaged contents. The examination shows a commercial control of mold and mildew in the fumigated raisins with many of the unfumigated and packaged raisins showing a heavy growth of these organisms.

The fluorobutene compounds as employed in accord ance with the present invention may be prepared by known methods disclosed in the J our. Amer. Chem. Soc, vol. 69, p. 279 (1947). For example, equimolecular proportions of l,1-dichlo'ro2,2-difiuoroethylene and monochlorotrifiuoroethylene may be heated together under autogenous pressure and at a temperature of about 200 C. to produce a 1,1,2-trichloro-2,3,3,4,4-cyclobutane prod act which may be separated from the reaction mixture by fractional distillation under reduced pressure. Dechlorination of the latter product with Zinc and in the presence of absolute alcohol yields 1-chloro-2,3,3,4,4-pentafluorocyclobutene. In a similar manner, 1,1-dichloro- 2,2-difluoroethylene or monochloro-trifluoroethyiene may be separately heated under autogenous pressure and at a temperature of 200 C. to produce 1,1,2,2-tetrachloro- 3,3,4,4-cyclobutane or 1,2-dichloro-1,2,3,3,4,4-cyclobutene, respectively. Dechlorination of these products with Zinc yields 1,2-dichloro-3,3,4,4-tetrafluorocyclobutene or hexafluorocyclobutene.

I claim:

1. A method for controlling insects, bacteria, nematodes and fungi which includes the step of exposing matter infested with these organisms to a lethal concentration of the vapors of a member of the group consisting of hexafluorocyclobutene, l-chloro-2,3,3,4,4-pentafluorocyclobutene, and 1,2-dichloro-3,3,4,4-tetrafluorocyclobutene.

2. A method which comprises the step of furnigating grain and its milled products with a member of the group consisting of hexafluorocyelobutene, l-chloro-2,3,3,4,4- pentafluorocyclobutene and 1,2 dichloro 3,3,4,4 tetrafluorocyclobutene.

3. A method which comprises the step of exposing grain and its milled products to the vapors of a member of the group consisting of liexafiuorocyclobutene, l-chloro 2,3,3,4,4 pentafluorocyclobutene and 1,2 dichloro- 3,3,4,4- tetrafluorocyclobutene, the exposure being carried out in an enclosed space and with an amount of fluorine compound sufficient to provide a concentration of at least 0.2 pound per 1000 cubic feet of said enclosed space.

4. A method which comprises treating grain and its milled products with a composition made up of an organic fluorine compound as an active ingredient uniformly associated with an inert diluent as a carrier therefor, the treatment being carried out in an enclosed space at a dosage of at least 0.2 pound of the fluorine compound per 1000 cubic feet of said space and the active ingredient being a member of the group consisting of hexafiuorocycolbutene, 1 chloro 2,3,3,4,4 pentafluorocyclobutene and 1,2 dichloro 3,3,4,4 tetrafluorocyclobutene.

5. A composition comprising as an active ingredient a member of the group consisting of hexafluorocyclobutene, 1 chloro 2,3,3,4,4- pentafluorocyclobutene and 1,2-dichloro 3,3,41,4 tetrafluorocyclobutene dissolved in a volatile organic solvent, the active ingredient being present in the amount of at least one percent by weight.

References Cited in the file of this patent UNITED STATES PATENTS 1,956,620 ODaniel May 1, 1934 2,424,520 Tonkin July 22, 1947 FOREIGN PATENTS 920,161 France Jan. 2, 1947 OTHER REFERENCES U. S. D. A. Tech. Bull. 162, March 1929, pages 1, 2, 36, 46 and 47. 

1. A METHOD FOR CONTROLLING INSECTS, BACTERIA, NEMATODES FUNGI WHICH INCLUDES THE STEP OF EXPOSING MATTER INFESTED WITH THESE ORGANISMS TO A LETHAL CONCENTRATION OF THE VAPORS OF A MEMBER OF THE GROUP CONSISTING OF HEXAFLUOROCYCLOBUTENE, 1-CHLORO-2,3,3,4,4-PENTAFLUOROCYCLOBUTENE, AND 1,2-DICHLORO-3,3,4,4-TETRAFLUOROCYCLOBUTENE. 